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Re: AIX slow buffer reads

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Brad Nicholson <bnichols(at)ca(dot)afilias(dot)info>
Cc: Greg Smith <greg(at)2ndquadrant(dot)com>, André Volpato <andre(dot)volpato(at)ecomtecnologia(dot)com(dot)br>, pgsql-performance(at)postgresql(dot)org
Subject: Re: AIX slow buffer reads
Date: 2010-10-27 22:44:59
Message-ID: 29868.1288219499@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Brad Nicholson <bnichols(at)ca(dot)afilias(dot)info> writes:
> On 10/27/2010 4:10 PM, Tom Lane wrote:
>> AFAICT from googling, AIX does have posix_fadvise, though maybe it
>> doesn't do anything useful ...

> If there is an easy way to check if it does do anything useful?  If so, 
> I can check it out.

If you don't see any performance change in bitmap scans between
effective_io_concurrency = 0 and effective_io_concurrency = maybe 4 or
so, then you could probably conclude it's a no-op.

			regards, tom lane

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